Goodwill and Other Intangible Assets, Summary of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Summary of core deposit intangibles and other intangibles
Amortization of other intangible assets	$ 2,686	$ 2,233	$ 7,237	$ 5,926
Core Deposit Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	80,730		80,730		$ 58,100
Accumulated amortization	(10,438)		(10,438)		(5,326)
Net book value	70,292		70,292		52,774
Amortization of other intangible assets			5,112		5,326
Additions during the period
Summary of core deposit intangibles and other intangibles
Additions during the period			22,630		58,100
Other Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	44,887		44,887		44,931
Reductions due to sale			(140)		(43)
Accumulated amortization	(23,950)		(23,950)		(21,825)
Net book value	$ 20,797		20,797		23,062
Additions during the period			0		10,359
Amortization of other intangible assets			$ 2,125		$ 2,833